In recent years, improvement in fuel economy of a direct injection diesel engine has taken place by reducing a cooling loss by relatively reducing a gas flow in a cylinder. However, soot tends to increase due to poor mixing caused by small gas flow.
To deal with such a problem, a Patent Document 1 discloses a direct injection diesel engine using a fuel injection nozzle having two nozzle hole groups whose inclination angles with respect to a cylinder center axis line are different from each other, one is a large inclination angle and the other is a small inclination angle. Here, as compared with a penetration force of one of the two nozzle hole groups which is directed at an upper side, a penetration force of the other of the two nozzle hole groups which is directed at a lower side is set to be large. Further, these two types of nozzle holes are alternately arranged in a circumferential direction. With these setting and arrangement, fuel can be widely spread in a combustion chamber and the soot can be reduced.
In addition, also in a Patent Document 2 that concerns a methanol engine using methanol as fuel which is not capable of being compression-ignited, a fuel injection nozzle having two nozzle hole groups whose inclination angles with respect to a cylinder center axis line are different from each other, one is a large inclination angle and the other is a small inclination angle, is used. Then, a glow plug to ignite the methanol fuel is provided at a position crossing a spray center axis line of one nozzle hole of the nozzle hole group that is directed at an upper side.
In the case of the direct injection diesel engine performing the compression ignition, although a glow plug or an intake heater alternative to the glow plug is required for a cold start, there is no disclosure about an arrangement of the glow plug in the Patent Document 1.
On the other hand, the Patent Document 2 has a configuration in which fuel that is injected from the nozzle hole directly collides with the glow plug. In this configuration, there is a problem that durability of the glow plug becomes low. In addition, in the direct injection diesel engine, especially when performing the cold start requiring the glow plug, it is general that the cold start is performed in combination with a swirl in the combustion chamber. However, a following fuel mass which flows and comes along the swirl in the presence of the swirl is positioned at a relatively lower side in a height direction of a cylinder. Therefore, if the glow plug is arranged at a position corresponding to the upper side spray center axis line like the Patent Document 2, the glow plug cannot contact the following fuel mass. Accordingly, ignitibility in the presence of the swirl becomes low.